Detonation suppression piston for internal-combustion engines



Patented Dec. 1'5, 19573 DETONATION SUPPRESSION PISTON FOR INTERNAL-COMBUSTION ENGINES Albert G. Bodine, Jr., Van Nuys, Calif. Application February 25, 1952, Serial No. 273,275

8 Claims.

This invention relates generally to internal combustion engines and to means for suppressing irregular burning and detonation of fuel-air mixture therein. The invention is based on my discovery that detonation in combustion engines involves acoustic phenomena yand can be alleviated by means of certain acoustic apparatus used in combination with the combustion chamber.

The present application is directed to improvements in the eld covered by Patent No. 2,573,e 536, issued October 30, 1951, and entitled Engine Detonation Control by Acoustic Methods and Apparatus. The present application is a continuation-impart of my application Serial No. 252,813, filed October 24, 1951, for Engine Detonation Control by Acoustic Methods and .Apparatus, which latter application is a division of my parent application which resulted in said Patent No. 2,573,536. For a full discussion of the acoustic aspect of detonation in combustion, and my basic solution for controlling detonation in combustion, reference should be had to my said issued patent.

Only briefly stated herein, the present invention is based on the fact that detonation in an engine combustion chamber produces sound waves, a large part of which rise to high amplitude at resonant frequencies of the chamber, and on my discovery that the sound waves produce the various well-known and harmful manifestations of detonation. According to my basic invention, I inhibit or attenuate these harmful effects by interfering with or attenuating the high amplitude detcnation-induced sound waves, and this is done by use in connection with the combustion chamber of acoustic 4attenuation means made responsive to the frequencies at which the detonation induced sound waves build up to high amplitudes. One type of acoustic attenuation means broadly disclosed in my patent involved an attenu'ative conguration given to the upper end portion of the piston.

The general object of the present invention is the provision of an improved detonation controlling sound wave attenuator means of the class involving the piston structure.

Another object is the provision of a piston type of detonation attenuator which is improved as regards attenuative response to the offensive sound wave frequencies encountered in combustion.

Still another object is the provision of a detonation attenuative configuration on the piston structure which is improved as regards practicability, freedom from diiculty by reason of carbon accumulation, and ease of construction.

According to the present invention, there is formed in the side wall of the piston, in the area between the upper ring groove and the top of the piston, a multiplicity of cavities extending in a row entirely around the piston. These cavities function as Helmholtz resonator cavities. To furnish communication between these cavities and the combustion chamber, the land between the cavities and the top surface of the piston is relieved or set back slightly, that is, given a clearance from the cylinder wall of the order of .005 to .030. This clearance space constitutes the neck of the Helmholtz resonator. The cavities are made of one or more sizes to be resonant to the offensive detonation frequencies in the combustion chamber. These cavities function as resonant absorbers, and are effective when designed to respond to the resonant peaks of the combustion chamber, to completely kill or substantially attenuate the harmful acoustic eifects of detonation.

The invention will be better understood from the following detailed description of an illustral tive embodiment, wherein:

Figure 1 is a side elevation of a piston in accordance with the invention shown in the cylinder of an engine;

Figure 2 is a top plan View of the piston, and

Figure 3 is a section of the piston on line 3 3 of Figure 1.

An engine cylinder is shown at 7, opening into combustion chamber 8, and the piston of the invention is designated by the numeral 9. The side wall I of the piston is shown to have ring grooves II, and above the top groove, a setback circumferential land I2 extending to the piston top, the diameter of this land being slightly less than the diameter of the main body of the piston, so as to leave a slight clearance space, typically .005 to .020, between the land I2 and the cylinder wall I3.

Sunk into this land I2 cavities, here shown in two I5, the cavities extending in a row entirely around the land I2. The cavities are preferably relatively close spaced to one another, so as to achieve as much coverage as possible. They are of different sizes, calculated or selected to be responsive to previously determined resonant frequencies of the combustion chamber.

In the present embodiment, the cavities Ill, which extend half-way around the piston, are designed to be responsive to a fundamental resonant frequency of a test chamber, and they 'are a multiplicity of sizes, such as I4 and are in the nature of flat-bottomed slots, in length, 1 wide, 1A" in depth, and the ends are rounded, as illustrated. The cavities I4, responsive to an offensive harmonic of the test chamber, are round holes with flat bottoms, -13-6 in diameter, and 59e deep.

In operation, the sound waves generated in the combustion chamber reach the cavities I4 and I5 via the clearance space between the land I2 and the cylinder wall, the fundamental frequency wave being absorbed by the large cavities I4, and the harmonic by the smaller cavities I5. The device will be seen to operate in the nature of a Helmholtz type resonant absorber, the cavities I4 and I5 comprising the chambers of Helmholtz resonators, and the clearance space between the land I2 and the cylinder wall I3 com prising the neck. The sound wave energy of detonation is thus absorbed by resonantv attenuator devices, designed to be responsive to the offensive frequencies of detonation, which are the acoustic resonant frequencies of the combustion chamber. By suppression of these resonant frequencies, the acoustic basis for the phenomena of detonation is effectively stifled.

It will be understood that the drawings and description are illustrative only, and that various changes in design, structure and arrangement may be made without departing from the invention as defined by the appended claims.

I claim:

1. A piston for an internal combustion engine having a cylinder and a combustion chamber, said piston having a cylindrical side wall formed with a setback surface at its top end, so arranged as to afford a narrow clearance space between said surface and the confronting surface of the cylinder of an engine in which said piston is installed, and there being an acoustic cavity sunk into the side of the piston and arranged in communication with said clearance space, said cavity functioning as the acoustic cavity of a Helmholtz resonator, and said clearance space functioning as the neck of said resonator through which sound waves from the combustion chamber may reach said cavity, said cavity being frequency responsive to a detonation sound wave in the combustion chamber.

2. A piston for an internal combustion engine having a cylinder and a combustion chamber, said piston having a cylindrical side wall yformed at its top end with set back surface areas, so arranged as to afford narrow clearance Space between said surface areas and the ,confronting surface of the cylinder, and there being a series of acoustic cavities extending entirely around the piston, all arranged in communication with said clearance space, said cavities functioning as the acoustic cavities of Helmholtz resonators and said clearance space functioning as the neck for said resonators through which sound waves from the combustion chamber may reach said cavities, said cavities being frequency responsive to detonation sound waves in the combustion chamber.

3. A piston for an internal combustion engine having a cylinder and a combustion chamber, said piston having a cylindrical side wall formed at its top end with a slightly reduced cylindrical section affording a clearance space between said section and the confronting surface of .the cyl.- inder, there being an acoustic cavity sunk into the side of said cylinder in a position to communicate with said clearance space, said cavity Cil functioning as the acoustic cavity of a Helmholtz resonator, and said clearance space functioning as the neck of said resonator, through which sound waves from the combustion chamber may reach said cavity, said cavity being frequency responsive to a detonation sound wave in the combustion chamber.

4. A piston for an internal combustion engine having a cylinder and a combustion chamber, said piston having a cylindrical side wall formed at its top end with a slightly reduced cylindrical section affording a clearance space between said section and the confronting surface of the cylinder said piston having a series of acoustic cavities extending entirely around the piston, all arranged in communication with said clearance space, said cavities functioning as the acoustic cavities of Helmholtz resonators and said clearance space functioning as a single neck for said resonators through which sound waves from the combustion chamber may reach said cavities, said cavities being frequency responsive ,to det-- onation sound waves in the combustion charnber.

5. A piston for an internal combustion engine having a cylinder and a combustion chamber, said piston having a side wall, there being an acoustic cavity sunk into said side wall near the top end of the piston, and a setback formation on said side wall forming a clearance space with the cylinder wall of the engine establishing re,- stricted sound wave communication between said cavity and the combustion chamber of the enf gine.

6. For use with an internal combustion engine having a combustion chamber and a cylinder opening into said chamber, a piston adapted for reciprocation in said chamber, said piston having at its top end a circumscribing cylindrical surface spaced slightly from the opposed walls of said cylinder, so as to form a narrow sound wave passage, and an acoustic attenuative cavity sunk into the wall of said piston below said surface and communicating with said combustion chamber by way of said sound wave passage.

7. For use with an internal combustion engine having a combustion chamber and a c ylinder opening into said chamber, a piston adapted for reciprocation in said chamber, said piston having at its top end a circumscribing cylindrical surface spaced slightly from the opposed 'alls of said cylinder, so as to form a narrow sound wave passage, and a ring of circumferentially spaced acoustic attenuative cavities sunk in the wall of lsaid piston below said surface and communicating with said combustion chamber by way of said sound wave passage.

8, For use in an internal ,combustion engine having a combustion chamber and a cylinder opening into said chamber, a piston adapted for reciprocation in said cylinder, lsaid piston having at its top end portion a circumscribing circumferential surface of revolution spaced.r from lthe wall surface of the cylinder, so as to form a sound wave passage, ,and said surface having sunk therein acoustic attenuation means presenting an attenuative acoustic response to a detonation wave frequency in said combustion chamber.

ALBERT G. BOBINE, Ja.

No references cited. 

